Odd Even Linked List.cpp

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* oddEvenList(ListNode* head) {
            if(head == NULL)
                    return NULL;
            ListNode *odd= head,*even=head->next,*evenhead= even;
            while(even !=NULL && even->next != NULL)
            {
                 odd->next=even->next;
                    odd=odd->next;
                    even->next=odd->next;
                    even=even->next;                
            }
              odd->next = evenhead;
            
            return head;
    }
};